To the OP I totally know what your talking about.
Around here All the Cypress mulch says "Cypress Mulch Blend" And they never tell you what with. I even phoned the company on the bag and they had no clue.
In all honesty before I switched to a pain in the rear like mulch I would try a larger water bowl and a humid hide.
If your set on mulch then look at petsmart for reptibark. MOre expensive but it does give peace of mind.
Because I have 0 luck finding 100% Cypress mulch at any lawn and garden store.