A trade as it is suggested here will not work in my opinion.
I wasn't aware that the XL bell is not available in The States yet. Mine was delivered without the sieve/penetrated disk at the tip of the bell because they don't do this for the XL anymore. I used the penetrated disk from another bell and glued it into the XL bell, careful not to close any channels. Since I am in need for a larger bell, I thought I could model my own bell and do a 3D print.
Because the adapter for the [words=http://www.phallosan.com/shop/catalog/default.php?z=eNortjIxtVKyL0pNszWxMFcrSSxKTy2JL0hMT7U1UisoykyxtbBQSy4tLsnPjS8uKcrMS7dVsgZcMMpbEbo%2C]Phallosan[/words] pump is so complicated to model on Computer Aided Design software, I thought it is better to implement another pump system. However it is not so easy to find tiny vacuum pumps.
Update: Pictures from the XL bell can be found in the thread "My thoughts on [words=http://www.phallosan.com/shop/catalog/default.php?z=eNortjIxtVKyL0pNszWxMFcrSSxKTy2JL0hMT7U1UisoykyxtbBQSy4tLsnPjS8uKcrMS7dVsgZcMMpbEbo%2C]Phallosan[/words]: Progress Thread".