Ideally with RAID, you want same disks... ...this is one reason the likes of HPE and Dell dump their own firmwares on, so they can pick different OEMs, but end up with identically function/performance disks, and hotplug support.
BUt given you are (presumably) running off the onboard B1x0i software RAID device, you'll find it actually has little bearing. The B1x0i isn't hotplug compatible IIRC, and the microserver's drive "backplane" (just cables IIRC) certainly won't be.
250Gb drives are quite hard to source now, especially Enterprise ones. Bro replaced an entire G6 server due to cost of drives (and the likelihood more would fail, and it was getting well past its sell by date - and the day before we decomed it, the array battery failed, so good call).
I may have a NHP HP/HPE 250Gb SATA drive somewhere, as some of OOF's servers came with them over the years, and they wouldn't have been used. Post up the HP/HPE Part number (Bxxxxxx-xxx) and I'll check. Yours for postage if I have one.