Here are both options - on my HK93 I went with the 'lower cost alternative' ambi group, which was still almost $400. On my SP89, I installed the ambi safety on a Navy style S-F housing utilizing the OEM semi trigger pack, which totaled about $200. The HK ambi housings have a bigger hole for the safety, and only fit the ambi trigger packs. The smaller hole housings will fit OEM, non-ambi trigger packs.
https://i.imgur.com/Es9IaYc.jpg