I would say it is a KVA . Here is a picture of one of the early gt40 replicas in germany ( HERMSEN GT40) . As far as i know ( and you can see it on the chassis construction of rear suspsension) it was based on a KVA kit. The pic shows the same rectangular corner shape of the side window.
KVA is out of business, but usually windows from every supplier are cut oversized, so you should be able to make them fit. for the Front Window probably most replica mafucturers windows will fit, because most of the current Kits have their roots somehow connected to KVA. So ask Tornado, CAV; RF; CCV and so on. A RCR Window will not fit because the have a close to original shape which probably will not fit one of the named replicas and also not your KIT.