OK.......Gluing on a fan just sounds dumb to be honest. What size fan/mounting does it have? If its something like a normal 40mm fan, and it uses say a 2 or 3 pin fan connector then no problem. You can buy a little fan and splice the wires to fit properly into that other socket. Pull the pins out of the fan connector on the new fan, and insert them into the plastic shroud of the old one.
This only works if...
1. The fan isn't recessed into a cut out of the heat sink and sits on top.
2. The fan uses the same style headers (for the most part)
3. If the new fan is the same voltage.
I've done this on a Dell server for the CPU and a few old video cards back in the day. You can also cut the wires on the new and old one and solder/twist them together with electrical tape, completely up to you.
If the owner is Ultra Stubborn, you can always look to http://www.frozencpu.com
for replacement heat-sink/fans.
Something like this... http://www.frozencpu.com/products/11754 ... 02-RD.html
$19.95, if that suits their needs and is acceptable, probably cheaper than buying a dead 3650 on eBay and hoping its fan isn't on the way out.