I use a generic Sondico wallet (Referee set) that is available on Amazon for something like £3. It has the paper record inside the wallet, with the cards outside of it, and a firm writing board within the cover.
I'd steer clear of anything that puts the paper on the outside (it'll get wet) and anything that's not firm (you'll be using the player's back to write their cautions on) and I wouldn't really pay a premium for them without some serious recommendations tbh, you don't need anything branding itself as 'fifa approved' or whatever.
The modern alternatives are the write-on/off cards, which I think are sold on this web's store, if it is still around (I haven't looked for a while, sorry.)