Back in 2017 when I was heavy into this hobby, buying up all guns and parts I could afford. I started to notice changes with HK's supply chain and it wasn't until 2019 when I got confirmation of that. I'm going to give you guys the inside scoop on HK's revised business model and it does NOT include supporting civilian sales to the extent some people are indicating. Buying parts from HK's customer service is not a priority and if by mere chance you land yourself a $30 rear sight, consider yourself lucky. Chances are they had a few extra pieces because one of their dealers put in a "large order". Otherwise, you're going to be on backover for over a year or they might just cancel it because they are not going to import just 1 sight to fill an order.
If you have not noticed all our favorite HK dealers have slowly increased their prices since 2018. Why?
Well, the "large order" is needed on the HK-USA side or else it's a no-go from HK Germany. Germany is still making parts on certain platforms (mostly current models) and they will still be available for LE and Defense business only, but they will no longer import parts in small quantities for civilian sales.
What HK has done is limited the supply chain to increase efficiencies that lead to profits.
Oh, and by the way, the few remaining sights @Saab95v6 has left, you probably should buy one now. God knows when the next shipment comes in. HK's supply chain has definitely become more unpredictable these days.