That's the kiddy Myron and this appears to be the best price (inc P&P) on fleabay at the moment :
https://www.ebay.co.uk/itm/GUNSON-TO...EAAOSwAaJaKR3C
I pushed my spare up to 40spi before starting each leg, seemed to work better although they recommend about 20psi but it soon drops off as you use it.