While they are the cheaper option they don't last as long so I am trying to find out if anyone produces NiCad batteries or if we have to buy the standard Bell part.
You can source the "original" battery from the manufacturer of the battery through FAA PMA and their distributors.
Bell Helicopter 407,427,430
Type TSP-283
Part No. 31908-001
PMA Supplement 50 (7-1-2005)
I once had to replace a battery in an EC135 (SAFT) in the US. Only source in the US was (then) EC. Quoted USD 22K.
Bought one from supplier in EU USD 8K. Released with a Form 1 with all the necessary paperwork for application.
Google the part number you will get a huge response.