My shoebox container are as big as a 10gal. They're also 3$ each and comes with a tight lid. You really want two because like I am saying, you want to have a spare one when moving the frog because where are you gonna put the frog while you clean your 10 gal? You can very well get 2x 10gal but now we're talking 25$ if not more with the lids... plus they're no where near as easy to clean as a light plastic container!

I think not moving a frog because of stress being the reason in this case isn't a good idea. Obviously any manipulation you do to an animal will stress it, change of environment do that too but I firmly believe most of the stress comes from the initial manipulation which is why I like to have spare Q box. I never manipulate my animals other than that and I also try to minimize my movement when in front of more stress sensitive animals vivarium.

If done properly, afterward stress of being moved can be totally ignored because treatment and sterile environment prioritize over prior issue.

I've saved frogs with similar blisters before with Q box and neosporin without pain killer successfully but if you can afford vet and really want to give best care for that animal then you should, RETF are very sensitive animals.
I'd try my shot myself but if it doesn't get better within 2 days I'd be real worried for the animals life.