Where to order milling and turning works and buy metal for your devices in St. Petersburg?

Question

Frame

In general, an interesting order was received, for its implementation it is necessary to cut a tricky pipe with a radiator from a stainless steel bar.
Where can they do this if I am a private person?
The first batch is single and trial, so it is necessary that someone accept such an order, and the purchase of a small amount of metal, and cutting the desired shape from just one bar