I had originally done a long post with direct links, but the system seems to have eaten it! I'll offer a slightly condensed version with some ideas instead.
Portable tickler file: If you need a desktop tickler as well, search for Decoflex or Really Useful Box. I like the latter because you can fasten the top and take it with you. If you want a really portable solution (here I'm assuming that you'll only be transporting a portion of your ticklers, because 43 folders can take up some room) you could try a simple document wallet like this, although you can get them anywhere. The idea is that you would take the folders you need from your tickler, stick them in the wallet, and bring them back when you return. If you want to carry all your ticklers, you could probably fit them into a legal wallet.
As for the folders themselves, I would look for "square cut folders" and get a decent thick card and ignore the brand names. The main point of manilla folders in the GTD system is that they're cheap and easy to find (in the US, anyway) and offer a large area for labelling. You can fulfill those requirements with square tabbed folders, though they don't look as nice, and you'll be paying £5-10 per box compared to £25-35 per box for the Avery tabbed folders.