Looks to me like a knock-off of a NH-55 rake (Straight axle).
That means bolts, teeth and tooth cups from TSC. Good excuse to buy 18v impact driver for quick change of broken or missing parts. They're asking $1700 on machinefinder.com
You need a rake even if your mower will windrow, IMHO.
I prefer this type of rake over a spinner (I have a Kuhn rake/tedder combo) because the roll-a-bar will rope the hay into an easy feeding stream to the bailer. This means that if you run into a windrow thick spot or a joint with another row, the baler can pull the rope in at a comfortable feed rate. When the hay is clustered (as the Kuhn does). The hay is all loose and the baler charge can get big real quick. This can result in a UBPSPR condition code situation in the baler control module. (Unexpected but Probable Shear Pin Replacement). This is often followed by a loud bang and a secondary expletive deleted phrase invocation at the main operator station .....