[OXO cube]

hi guys 
bought one of these a while back 
   
it did seem to do a good job 
it came with some clear plastic squares to vac form with 
but these were/are quite thick and too soft/flexible for screens/interiors etc 
so set it aside as an indulgent investment . but would like to to resurrect it
 
i was wondering what material everyone else uses for their vac forms ?
i am not the best when it comes to chemical compounds/plastic types or even internet searches . so links to specific products would be ideal in my case please

thankyou in advance 
Kev 

btw . UK based . therefore EU and other areas would sadly bring high shipping costs