Craigslist, junkyards, pretty much anywhere...the B18B1 engine is a cheap engine compared to some other Honda engines and non-Honda engines.
How much money will be 'hurting your pocket"?
Anywhere. Lot of junkyards have some sort of guarantee also. Should find one easily for less than $500.
And it depends on if you want a nice runner or something to rebuild.
Next time, post in WTB.Haha.