Welcome to the forum Max. Yes, addictive indeed!
I am afraid that you question about finding a keris coteng can't really be discussed in much detail here as commercial conversation is banned on the forums. After you get through that probational period and are eligible to use the Swap Forum section you could post a "Wanted" request there. I can't point you to specific internet dealers, but they are out there and a Google search for "keris" will no doubt bring up a few hits to explore. Nice old Coteng keris do seem to be a bit scarce though so not every dealer will have one. I do see them from time to time on ePray, though that is a dangerous place for beginner collectors for sure.