I'm looking for suction cups that are compatible with the Lego pneumatic system. I've seen people who have built things with them (on youtube videos, etc), but haven't found anything on eBay or BrickLink. Short of drilling a hole in a normal suction cup and popping a pneumatic tube into it, is there anything out there I could buy?
Basically they are usually found in DIY/Home stores as metal or plastic hooks wrapped around a transparent suction cup so you can easily affix them to tiles or windows.
There is also a picture showing three variants that were tried, with the preferred option being those in the bottom left I think:
Depending on the weight of the model you've got you may also need to invest in some additional custom air bellows: