Thanks Errol your a champion. Rare spares is the go and $4 is a good enough price just don't like the $10 postage. It said to pm them for postage cost as well so maybe they will drop the price?
I think the 3/16 will the the go. That's almost 5mm, the old ones where 6 mm ID the post is just over 5mm so that seems like the safest bet.
I should have them (or another) ordered soon and I will let you know how they go.