Waterproof Portable Storage Options?

I can vouch for Kriega stuff being robust and 100% waterproof and the US-20 and 30 come with shoulder and waist strap for carrying it off the bike, see Revzilla review. (I've not used it that way so can't say how comfortable it is).

Edit: It sounds like you want a backpack that can attach to bike, not those tailpacks I have that may be pushed into service as backpacks.

 

Yeh, I did look for info on that. Don't know if the plastic clips on them (for depth adjustment I presume) are the same size as the clips on the tail bag fixing straps. Some of the rucksacks do seem to have a pair of tags either side which may be pressed into service for lashing down to rear seat.

I don't know if there's any shop you could go to have a look at them to get an idea. Or if there's any shop that does free return for kit you don't want. (I'm lucky in the UK that I have both.)

 

Hard luggage. Secure, watertight, don’t need to carry your stuff around, it’s not hanging on your back whilst riding but it’s not cheap.

 

My Triumph expedition panniers have so far been 100% waterproof. I live in Yorkshire so ride in heavy rain a lot. As for security, panniers are a damn site harder to break into than soft luggage which just requires a knife or pair of scissors. I also filter every day, for mile after mile sometimes. The bars are the widest part so if they fit then through we go.

 

I use a Kriega backpack. It's comfortable and I barely notice I'm using it while riding. It's claimed to be waterproof. It isn't. After a couple of hours in heavy rain (in good ol' Yorkshire) I found my stuff was slightly damp at the top, near the zip. I guess I was a bit naive to believe any soft luggage can be 100% waterproof when exposed to prolonged heavy rain.
Before I had the Kriega I always put my stuff into plastic bags, inside whatever luggage I was using. From now on I always will. Lesson learned.

Incidentally, I have occasionally used soft panniers and strapped small backpacks to the pillion seat. I have often left these on the bike when going walkabout. In all the years I've done this I have never experienced any issues with theft. I would not be so stupid as to leave anything particularly valuable, only things that are replaceable, and I'm always careful about where I park the bike (I do that regardless). Maybe I've just been lucky.
Having said that I only leave soft luggage on a bike overnight if it is totally empty. Again, never had a problem.

 

Have a look at Lomo to see if there's anything suitable for you by them.
They are predominately watersports specialists, but over the years have been expanding the motorcycle range as everything is 100% waterproof!

https://lomo.co.uk/acatalog/Motorcycle-Motorbike-Dry-bags-Accessories.html

 

The Aerostich Messenger Bag is waterproof and you’ll never know it’s on. Big enough. Very well made.
The way it’s designed it doesn’t flap about. Seriously - you’ll never know it’s you have it on.

 

I have a small Kriega US10 for day trips. That range come with for straps for attaching to the bike and have dry bag style roll top for the waterproof section. These are great kit, but not the cheapest.

I also have a 30l white Lomo holdall style dry bag with a shoulder strap. It also has the roll top design, you squeeze air out before rolling and clipping shut. These bags are ridiculously cheap (~£35), simple and effective. Easy to strap on the back with crossed over ROK Straps that have been jiggled and tightened (~£15). I use this for a 100m each way commute, it's cheapest and most effective system for commuting that I have ever had. 2 hours would be about the limit for walking around with it over the shoulder I would think. This is no good for situations where you would want to leave on the bike somewhere as it is unsecured.

 

I love the Lomo stuff - the qualityrice ratio is *almost* unbelievable - I expected my bag to fall apart/wear out years ago yet its still good

 

I highly recommend Kriega. I have the 30Lt & 20Lt drypacks which clip together simply & securely. The drypacks are fully waterproof & come with a 10 year guarantee. They also make for a comfortable back rest in this setup.

 

Probably not secure enough to leave for a couple of hours. The Kriega backpacks are however comfortable to wear & may be an option to take with you on your hike.
https://kriega.com/riderpacks