In France it is getting difficult to find 25CD4 (25CrMo4), because for most applications everyone moved to 15CDV6 which has higher strength and better weldability. It doesn't behave exactly like 25CD4 regarding hardening and tempering so it is not always the right answer but a lot of people use it for engine mounts for example.
A lot of the tubing that ACS sells is made in Germany by Benteler.
Meracing.com in Sweden sells 4130.
Regarding 15CDV6,or 1.7734.4 in Germany,I think it sells for above 50 Euros/meter.It is used on all the Extra planes.