I wanted one as well. I really struggled. Pros have them and you can get long sleeve skin suits so why you can’t get a decent long sleeve jersey is beyond me. I wanted one as I occasionally wear a long sleeve baselayer underneath when arm warmers don’t quite cut it.
I have one from Northwave that is good. But they aren’t very common. Got it from start cycles.
I have a really cheap one from cycle-clothing.co.uk which I use for CX training and warmups as it gets trashed.
I notice that wiggle are doing a dhb aeron one. Most of the rest of the DHB kit I’ve found to be really good (and fitted). They were about £44 this morning as there was an offer on.