While spelling doesn't count much anymore, it is helpful when looking up parts and trademarks. Also it is important to have all 7 digits-letters in 7 digit part number in order to find it.
The correct spelling is Pozidriv; also part no. is 2222A14 Miniature Electronic Pozidriv Driver Tip #1, 2-23/64" Blade Length Re: Posidrive #1
There's a source in the archives; here's another for the Posidrive #1 driver - I bought mine last week via Internet from McMaster Carr - www.mcmaster.com. Part number 222A14 $3.60 each and $3.75 shipping.