Ability to buy 'One off' AI credits

Ability to purchase an (additional) ‘block’ of AI Credits without having to upgrade your plan.

Normally I find my current plan gives me enough AI credits for my needs. However very occasionally I have a project that requires a few more than my normal monthy ‘allowance’ under my plan.

It would be really useful to be able to buy a block of additional credits that could be added as required.