Couldn’t find this information on the forum aside from people that bought them in bulk directly from HellermannTyton and were selling the extras on the marketplace.
You can buy the same curved/flexible adhesive zip tie mounts in individual quantities here https://www.sager.com/151-01527-5514015.html
They don’t list shipping and don’t charge you for it till after the fact but it was $14 for 12 of them.
Description since they don’t list it on the Sager website:
HellermannTyton FlexTack Adhesive Cable Tie Mounts deliver excellent mounting performance on flat, curved and moderately angled surfaces. Use in combination with 18- through 50-pound cable ties to provide stability when securing bundles.