Frage Machine T-Nuts/Bolts for Aluminum Table

Even if it was a bit costly for the SC2-600 size table, I'm glad I purchased w/ my original kit. Because of the unique width/depth of the t-slots, I have had difficulty finding perfect-fitting T-slot nuts/studs/bolts so I could mount 4 adjustable hold-down clamps. I have been able to get by with M6 hex head bolts, heavy rubber washers, etc., but would like to find a source in the USA if anyone has a recommendation. Thanks.

The T-slots are standardised; it's just that the small size is uncommon.

Try searching for the standards:
Nuts DIN 508
Studs for above DIN 6739
Bolts DIN 787

Of course there's many more parts and accessories to M6 slots, but the above should help you find them.

Search times according to DIN 562 , plus a normal M6 screw in the required length, then you have everything you need.