boating stores (used for trailors and decks for traction)
hardware stores (not all, but some will have the black/yellows caution type grip)
skate shop
internet
The first two will be your best bet - since it will be designed for being stepped on, weathered, and the like.
Skateboard friction tape will be a second, since it's probably not designed as much for weather as the industrial stuff (the adhesive on indistrial is better-designed, since it's also solvent-resistant, detergent-resistant, ...)
Another option would be to paint the fenders with the stuff they're
supposed to use on cement in parking garages and on walkways - it's an epoxy-based paint with sand mixed in, so you're getting traction all over and can get it in a few different colours. Check industrial supply houses for that stuff.
(I say "supposed to" - when Adobe moved into the tower downtown, the guy that signed off on the plans was an idiot. Drainage in the subbasement parking levels sucked (there was storage down there, but I wasn't going to use it right away. My actions were validated for the first rain - B2 flooded seven feet deep...) and he didn't specify the "sand paint" in the garage. I didn't park in the garage in the tower when it rained, since I also had a card for across the street (and they used sand paint in there.)
The first rainy day after the tower opened, I think I saw something like eighty incident reports written for people sliding into each other in the parking garage - mostly on the ground floor-to-level three ramp...
Funny thing - while the building was going up, I'd gotten a good look at the prints. Had a notepad with me, and wrote down everything I thought would be a problem in the future. Dated the list, copied it, and mailed it to myself (to fix the date on the thing.)
After most of the predictions had come to pass, I gave the unopened list to the VP who'd signed off on it, and who I'd talked to about changing things before it became a problem.
He opened the list, and read about how I'd predicted damned near all of the problems that had come to pass...
The money he'd saved in not running the freight elevator down to B1 and B2? Made up for that in WC claims for back injuries having to push loads up and down the ramps (couldn't use the pax elevators into the garage.)
The money he'd saved in not using sand paint? More than made up for in having to pay out auto damage claims.
I'd told him to put in booster sump pumps to drain B1 and B2. He didn't. I ended up swimming around down there to clear the drains - for which I charged (and ended up getting) triple-time for the hazzard. Not to mention the damage claims from flooded vehicles, and the wrecked equipment (mostly from people who'd had some sense to ask me why I wasn't using my big closet down there, but didn't listen when I told them it would flood with the first big rain...)
There are times I really
hate being right...
But, I digress. Find yourself a quart of "sand paint" as used in parking garages. If you can't find it already mixed, a major paint store (that caters to contractors and such) should be able to help you. Probably the best possible fix going - the epoxy paint is Hell-for-strong, and you don't have to worry about tape peeling up on you in a few years (if the paint starts to peel; just sand, feather, and repaint. That won't be anything more than every 12-15 years tho, I'm fairly sure. Maybe you should buy just a pint of the stuff, if you're only doing the fenders. It would probably go solid in the can before you needed to use it again.)
