Calcium carbonate, most likely, can be used (as far as I know, weak acids will react with CaCO3). You'll have to follow this sort of baking soda method, and you may have to extend the time of reaction to 24+ hrs. I've never personally tried it but it's worth attempting.
Rhodium, here's a sample write-up for addition to your faq (I wasn't sure if you wanted me to follow your #s or #s that I have personally used, whatever, the rxn and results will be the same):
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Add 273g NaHCO3 (3.25 moles of baking soda) to 1125ml distilled water in a glass container. Slowly bring the solution to a boil while stirring with a glass rod or similar. All of the baking soda will dissolve. Carbon dioxide will be seen leaving the solution as it comes to a boil. This is the sodium bicarbonate breaking down into a slightly stronger base, sodium carbonate:
2 NaHCO3 -> Na2CO3 + H2O + CO2
Reduce the heat to a light boil, and slowly add 250ml gamma-butyrolactone (280g, 3.25 moles). The addition is not immediately exothermic as with the sodium hydroxide synthesis. Keep this solution at a light boil for 30 minutes.
Check the pH with universal pH paper. We are aiming for a pH around 7, but anything 6 to 8 is perfectly safe. If the pH is too high, add a small amount more GBL and continue to reflux.
The solution will be perfectly clear and should be absolutely colorless. If it is not perfectly colorless, i.e. if slightly impure butyrolactone was used and the solution has taken on a light yellow color, add about 100ml of activated charcoal. Allow this to boil for 10 minutes. Cool the solution then filter, washing the activated charcoal with 2 or 3 50ml portions of cold water.
410g of NaGHB will be made in this synthesis. This solution can be concentrated to about 50% NaGHB before it will start to crystallize. If you wish for a powder, heat until the temperature of the solution reaches 150C then pour onto a flexible metal sheet and allow it to cool and solidify.
This synthesis is perfect for use where there is no food grade, ACS grade or electronics grade sodium hydroxide available.