Fill adaptor

finish my airarms bullpup conversion, and decided to fill it up with air, i couldnt beleive it, looked all over the shed, garage house, garden, couldnt find my fill adaptor anywhere, looked on the internet to see how much it would cost to buy one, they cost about £19 so i though Sod That, ill have a go at making one, being as i could remember what it looked like, and this is what i ended up with, slightly different but works fine.