Most armor is subject to ITAR, you can't just send it to another country. You could send a plate carrier and helmet without running into ITAR problems, have them source ballistic plates locally.

Another thought, there are lots of other basics these guys need right now that most people are probably overlooking. Eye and ear protection are important, so are good boots and gloves. Also socks, send lots of socks.

second the boots and socks.

Your likely want to look for “Level 3-A” plates for armor such that it can take an AK round. These plates fit into a “plate carrier,” usually the camo outer layer with MOLLE for attaching whatever. Price wise you’re starting around $500 for a set of plate (chest, back, sides) (in America at least where these are common and domestically produced)

You can get further, with coverings for arms, neck, and groin though they are not quite as typically used.

As for helmets, more or less whatever your host nation uses for their military.

Kevlar helmets and ceramic body armor is pretty standard. Go for body armor that can take a hit from 7.62 rounds. Body armor is heavy so most people prefer the ones that don’t have plates on the sides and over the shoulders as an compromise between weight and protection.

Isn’t it better that you give money to the Ukrainian military though, so they can get what they need? How will you even get the equipment into Ukraine now?

Exporting body armor can be as regulated as weapons, look up about that first.

Recommend velocity systems scarab plate carrier, and something like hesco 3810 multi curve plates, back and front.

I wouldn't recommend side plates and groin as they greatly reduce movement, but if you're gonna stand around and get shot at, then maybe?

Opscore ballistic helmet if money is no object?

I doubt you can just FedEx it at the moment?