I would get a used one from eBay from a VN750 or Ninja 600. Just look at them to verify for yourself depending on the Ninja's year. Mine was $16 of a 90s Ninja 600, and is working great!
Edit: This suggestion is due to you wanting "cheap", which I'll take as "inexpensive". Cheap would lean towards the Chinese R/R's off eBay that come bad, or fail quickly.
1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Rebuilt Forks w/ Progressive Springs
VN750.com Grill Cover
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R
1990 Kawasaki Vulcan 750
1998 Honda VFR800 FI
2014 Honda VFR800F
1989 Pontiac Firebird Formula 350