I have a design for oval port I did a while ago for small injectors. I could revise it to suit standard size injectors so that it suits everyone. I did look at getting it machined (mild steel for me but would work in aluminium as well) the feed back I got was it would be a lot of machine time. One prototyping place we use at work quoted me $600-, can't remember if that was each or for the pair now but either way a bit steep so I started thinking about other options.

There's probably some images of it on the forum somewhere.