where and how much does a jib furrler cost
Depends on what size you need, the quality you're looking for (price too) and where you buy from.
If you want cheap, you can DIY a furler. There are quite a few posts about it, check out the search feature on the forum (use the word furler) for more info on how to make it. Less than $50 with supplies from Home Depot.
Mid-grade is the CDI Flexible Furler. Size FF1 for a 16, FF2 for 19/23. $475--$550 ish
High end is the harken 00AL or MKIV. $900-1300+new forestay
There are almost certainly others that will work fine (profurl) but there hasn't been a lot of discussion on them.
As to where to buy from, I like Defender.com but on more expensive things like this, it pays to do some internet shopping. I got the Harken from Defender for around $900 but it's now $1300 on sale.
Also keep in mind if your jib is hank-on, you'll need to either buy a new jib to work with the furler or have the jib recut to match along with luff tape to match the furler slot, so almost certainly extra cost there. However, if you're going to DIY, you can use what you have as others have done. Again, search the forum there is a ton of info on it, some posts are fairly recent.