>>1232192>>1232188Either option possible with pic related, $25
Front conversion would be:
$25 hanger pictured
$15 new chain
$15 second chainring
$15 chain tensioner
$10 front derailer
$5 double chaining bolts
(Assuming you don't need a new crank)
Almost $100 if you buy new. Most of that stuff will be available for very cheap or free at a bike co-op though, or removed from a free/cheap bike. Good luck