Hey.

Some time ago bought a copy of doom from a local game store on sale. After a few games the markings on the dice began to wear off and now you can barely make out any of the results.

Is there any way of getting replacements for these anywhere?

Not that I know of. Sounds like you have an early version of Doom. I believe the early editions had dice that were printed on, which rub off over time. FF use to sell Doom dice that were engraved with the logos. What you should do is buy indented/recessed dice and make stickers. There is a link on the FF website where you can find them.

http://www.fantasyflightgames.com/ffg_content/Doom/DoomDice.pdf

Hope this helps.