Sad truth, the DVD sets are being phased out. As technology advances, DVD’s were thrown into obscurity, being surpassed by Blu-ray’s in almost every way.
Kampfer does have a DVD release, but there’s 2 problems.
1st) The set doesn’t include the Fur De Leibe OVAS, so you’d have to purchase them separately (On DVD they had the OVA in it’s own set since it was licensed after the series was released on DVD)
2nd) The dub is exclusive to the new Blu-ray set (and HiDive, but that’s digital media, not physical)
You could always wait for the Black Friday sale. While being 6 months away, they should have it on discount for around $30 or so plus shipping.