This is just typical of what happens when you take your eye off the ball for a year or two.
The two places you could get the motor required now no longer stock such an item.
The motors on the link you have posted are "Brushless" requiring an ESC (electronic speed controller) - wow you've given me an idea for an everlasting scavenge pump!
Its better to source them local and actually get to see them in the flesh so to speak as shaft lengths can be differenf.
As i said the motor is nothing special and it sure
ain't 12 volts either - more like 6 volts, now you know why they expire so readily.
I bought some a few years ago from the Enfield Pageant (auto jumble) from a firm called Greenweld;
http://www.greenweld.co.uk/acatalog/Shop_Motors_53.htmlI cant remember the dimensions off hand but i think its Ref: CDT0008 but don't take my word for it double check with them first.
Proops Brothers were another supplier of such things (don't bother looking up their web page as they don't list any) but if you were to catch them at an event you would find the motor you require on their stand.