I got a replacement for mine a month or two back (1150 not 1100 but it's the same part....
here's the Motorwoks listing)
Mine wasn't bosch but it didnt come with the sock.....I'm pretty sure a replacement bosch won't either, as it's a BMW thing not a bosch thng if you see what I mean.
Motoworks do them for 24 quid (see above link) but I just washed the old one out and re-used it.
If it's of any use, the pump I got was part number FPTFP2098, cost 54 quid
It's a generic 3bar regulated in tank pump, also fits many audis and VWs.
The only minor difference was a bit of bending needed to get the bracket mounted to the filler plate to fit, then bending it back to hold the pump body again.
24 quid is a silly price for what is essentially just a petrol proof nylon bag
Go into any motorfactors with the Bosch part number (that's the reference they all cross to other brands in the books) and you can find them for down to about 35 quid (David Hale got his for £32 in a recent thread)
Unless your original sock is floating around lost in the tank (In which case it needs to come out anyway) or ripped up (unlikely) why not re-use?