I finally got around to doing this idea I had and thought I'd post it up for anyone else who may want to do this. I had a thread last year about sewing on a hip belt but decided to do this myself because it was too expensive to have someone else sew. And it ended up really easy.
So the first thing I did was grab an old cheap Fieldline pack I had that had the buddy lok attachments on the belt. I cut those off and used them to practice with. Also I have been looking for these online to buy individually and finally found some. These are designed to be sewn on with a standard machine but I just hand sewed them on with some outdoor specific thread (polyester). I first sewed the female end of the buddy lok onto a 2" piece of webbing. This is where a sewing machine would come in handy as I had to do this by hand and after doing a few, your fingers get pretty sore

After sewing the plastic female end on the webbing I then sewed the webbing onto the hip belt after careful positioning. Hand sewing this was much easier as the needle moved easily through the belt and webbing. I had a pocket on that side which I cut off but I don't use those hipbelt pockets much anyways. I also sewed on these to the other side so I can put pouches on the hip belt with buddy loks.
Anyways now that the hip belt end was done on this I moved to the holster. I tried a few different older holsters I had using rivets and it worked ok but I decided to buy a Blackhawk holster and see how that worked. It worked awesome. I removed the 3 screws on the belt attachment and using the male end of the buddy lok, I drilled 3 holes and put it in place of the original belt attachment. (Remember to mount the male and female ends 90 degrees off of each other). To make sure the holster does not twist out/off while hiking or getting snagged on brush when going through the thicker stuff, use one or two zip ties through the buddy lok when attached (you wont see these when trimmed off). So far I have tested this and it is strong and seems like it will hold up in the long term. I have put a female end on each side of the hip belts on all my packs so it makes it very easy and modular. Aside from the holster, this has cost less than $20.00 to do a day pack, hunting pack, and backpacking pack (six attachment points for holsters or pouches) and I have enough to do 5-6 more.
Anyways, here are some pictures of one of them.