Getting a bargain usually doesn't tie in with having a time scale I'm afraid.
I've got a Singular Swift and in November picked up a pair of (QR) Reba SL 100mm forks from On One for half price...but that's because like you I wouldn't pay £500 for them and waited 5 months until they were shifting stock.
How about getting some On One or Exotic rigid carbon forks for < £100 for the moment, then keep your eyes peeled for the bargain fork you want (On One, Merlin are usually good, also watch the Singletrackworld forum for heads-up posts about bargains). Then sell the rigid fork for £50.
Of course, if you've already got the bolt-thru wheels then these won't work with the rigid forks suggested...
For what it's worth, I've put my Singular steel forks back on the Swift for the moment. They're brilliant. I'll give the Rebas a good run out through this summer, but don't right off rigid forks on a 29er if you're using it for XC stuff.