I agree, i don't see how it would be done without the proper hardener.
I purchased mine from http://www.dansonmarine.co.uk/ and he shipped 2 packs to Spain for 17GBP for 3-4 days.

Maybe buy locally the epoxy and purchase only the hardener, have to check with them though.

For the Hiwin 20 rails the minimum width of the epoxy should be 40mm, that leaves 10mm each side of the rails, cause epoxy rises like 5mm near the edge. I made mine something like 5mm high. Used magnets 4.5mm thick at both corners both sides, to check visually whats going on and make perfect 5mm height


About the laser cut pieces, i dont see why they would charge more for the holes. I ordered mine with holes, that's was the whole point, to save time drilling precisely. Even the 4mm holes were perfect.