I got mine from my smash repairer who have a guy come out and replace all the windscreen's and seals..they are fairly stardard locking strips...they do go that faded brown colour after a few years of sun exposure...
Can't say how much they cost as he didn't charge me, they shouldn't be too much though, do make sure the first time you put them in (or someone else does) that at least 1 or 2 inches is left as once it's on the car it shrinks from sun exposure, leave it for a week or two in the sun, then cut off the excess to length
I think Mini Spare's Centre sells them, but it would probably be cheaper to get a bit cut off from a windscreen guy, it comes in a roll..