I need to find some heavy duty t-nuts with a 1/4-20 thread for 3030 aluminium profile. This seems really hard to find in the UK. Happy to order from elsewhere but I can only see these on sites in America and the postage is crazy.

Also happy to use any other hardware which will allow me to attach a 1/4-20 device to aluminium profile. It does need to be heavy duty though, the item I'm attaching is heavy.

Thanks in advance