Food grade silicone can handle temperatures between -80°F - 450°F. The isomalt directions say to remove from heat at 333°F, then plunge it into ice water where it will increase to ~338°F. So, anything that's made with food grade silicone will work with isomalt.

These molds are food grade silicone and close to youre desired measurement:

1, 2, 3,

I think 3 is the closest to your size, 1 might be the right size, but the diagram is very odd.