take the pushpins off stock cooler, and replace the freezer 7 ones (means cutting the ali and a bit of bending)
what about using 4x M3 40mm bolts, you'll need some plastic/rubber/card washers but very easy to make your own.
ever s775 waterblock uses this approach - as do all the backplate HSF combo's but I'll hunt out a pushpin/bolt mod photo for you.
Arctic cooling have a spare parts shop on a popular auction site.
Have a search for Item number: 270149994571
I think these are what you are looking for.
here is a good well photo'ed how-too
For a different HS but you see what I'm talking about - clicky
If you don't have a decent hardware store near you - these are a good alturnative
As a final note, many use nylon nuts/bolts as you have a bit of flex and zero conductivity
and also use an extra 'locking' nut on the top of the mobo so that you don't have to hold the bolt in place as you line up your block/HS.
Here are two images of what I used with my waterblocks
Twin blocks
Cheers, but with delivery etc i might as well pick up a cheap stock cooler.
Item number: 360070377623. 4 including postage works out at £3.99