I suspect you need something along a wheel bearing grease but the lithium types will work well too. Make sure you thoroughly wash out the old grease with solvent before repacking them, especially if using the lithium. Good idea when changing any grease brands anyway.
Does the manual just say Alvania, no mention of subtype?
I think Shell greases inc Alvania are now marketed as a range under the Shell Gadus name, used worldwide. Shell Gadus S2 V220 2 is the newname of Shell Alvania Ep2 Grease. However I still see some Alvania on the market.
It is absolutely vital that the bearing is cleaned perfectly. More damage can be caused by a little bit of grit than by negligence. Spin the dry bearing to check it is smooth running before repacking with absolutely clean grease.