Sorry but thats not true. HK Customer Service is very good from my Point of view.
I emailed them and got 2 Lense and Foam send to Germany fro free as recplacement. It took them Overall 4 Weeks, but they didnt had the Parts in for the first 3 Weeks. Heard from other People that they recieved it nearly same time.
If you only got one Lense, then you probably didnt told them, that you have and needed more then one Lense.
For Bottom Foam - there is no new "exchangeable" Bottom foam, therefor they dont replace it.
To reglue it once and for all is quite easy - roughen up the Plastics (either use rough sandpaper or a use a knife carefully) - use either a good contact glue, or specific Plastic glue afterwards.
If you dont have any, ask at your Local field where they have Rentals. (They have to fix the rental masks quite often)
HK didnt do a perfect Job on the Foam glue, but on the other side, the Mask is extremly easy to clean from paint rests.
Once the foam is properly glued, it stays on