Yea, link above "Tested Memory List" gives you part numbers, search for the part numbers. Use google's "shopping" page, order by price, avoid scammy looking places. I did exactly that for a X9-SCM, got Hynix ECC memory from Superbiiz who had the lowest price+shipping at the time, worked a treat.
If you're really willing to trade time for trying to save bucks, search each part number you find at each store site - Amazon, Newegg, the various memory sellers, etc. - google's shopping page doesn't always get the current price or take into account specials/coupons. Possibly plug the motherboard model into the various memory vendor's configurator - crucial, kingston, etc, that will give their suggestion of compatible memory part numbers, go search *those* part numbers. But of course you're a step off the comfort of the "Tested Memory List" - there's lots of other memory that will work but it's a little more of a gamble...