The reason the XD Gear package for the Sub-compact was hard to find for awhile is that for the first month, January, Acusport had an exclusive with Springfield on the package. I ordered 4 of them through Acusport (all sold) at the SHOT Show and they were delivered before I got back from the show.
On February 1st, the package was released to the other distributors, so it should be more available now. The next package, which I believe is the Service, but don't hold me to that, is also an exclusive for the first month, but with another distributor. The Springfield rep at the SHOT Show told us there were four different packages and each was going to be exclusive to a different distributor for the first month of issue.
The grip fillers are not scheduled to be released for sale separately at this time, even though I practically begged them to release them. All their supplies of grip fillers at this time are being used to make the XD Gear packages for the SC. When they catch up on those orders, the grip fillers will be sold as a package with a hi-cap magazine, but not separately.
This is what I was told in the Springfield booth at the show last week. They said that sometime in the future, they may be able to sell the grip fillers to dealers, but they had no idea if, or when, this would occur.
I talked at some length to a couple of reps about how well the grip fillers match the rest of the frame, unlike the Witness grip fillers for the Compact frames. They told me the prototype was cut from the grip of a large frame pistol and fitted to a SC. Then they made the mold and started casting them. They had to rework the mold a couple of times, because the original fillers were the same size inside as the mag well, and fell off the magazine when it was ejected. They made them fit tighter and now the model they sell is a really snug fit and won't fall off. In fact, it's really snug. I forgot to ask them if that was done in the U. S. or Croatia.
Hope this helps.