Hi Ken,
here are a couple of 380-390nm + one 320 filter
ZB1 B390....reasonably tight around 380nm without much appreciable Red-IR pass response. Many sizes available all mounted
https://www.ebay.com.au/itm/27439485...r=574525500112
ZWB1.... reasonably tight around 320nm without much appreciable Red-IR pass response
https://www.ebay.com.au/itm/27439402...r=574524646322
ZB2....reasonably tight around 380nm with appreciable Red-IR pass response. Many sizes available all unmounted, but you could possibly use a 48mm filter housing and perhaps fit one of the 45 or 46.5mm unmounted filters in it.
https://www.ebay.com.au/itm/27392214...r=574524784290
Best
JA