There is a kind of "Multi-BX" from Tetenal which can be used for C-41 as well as E-6. It is avalable in 2 parts for 15L solution, but can be calculated down for smaller batches very easy. I always make 500ml of working solution. I use the same product, but separate working solution for E-6 and C-41.
I use it since 2 years and it works fine.

My bigger problem is, that there is no separate first developer available in small bottles. Color developer and BLIX last for a long time but the livetime of the FD is limited.