Hi Joanne,
Interesting concept about using SPXS for egg-bound reptiles. Are they classed as Kidney deficient? Certainly it would be a good source of calcium.
K'an makes a liquid version in their Traditionals product line. I can't recall the name. Mona Boudreaux at atthherbs@aol.com can supply a powdered version, I'm pretty sure. Orally administered. Use the same dose, pro-rated down, as you would for small animals, to a minimum of 1/16 tsp or about three drops, given BID. The powdered versions probably have more calcium.
Hope this helps you out!