I'm pretty sure there are some available but can't state specifically if Tractor Supply or Rural King carry them. I know Everything Attachments sells them though.
The thing about the 1023 and 1025 is the limited category 1 three point will only allow a 36" long auger.
The Land Shark brand at EA sells for around $750 including the auger with free shipping.
All of the common Cat 1 post hole diggers will work. The issue you need to deal with is the limited lift height. So you need to look for auger bits that are shorter. I've seen bits come in 36", 40" and 48" lengths. If my memory serves correctly, you need the 36" auger bits for the 1-series machines.
Here is the County Line auger from Tractor Supply on the 1026r that I had. This is the "standard" length augers, but they make some shorter than these. To get the height, you have to use the hole on the boom closest to the tractor, so you have the least amount of lift capacity, so you want to clear the auger often and do your best to keep it from screwing in.
I went to Harbor Freight and bought the reverse kit for it too :laugh:
Pro Tip, if you have to unscrew it, disengage the rear PTO...It's a whole lot easier to turn. Ask me how I know.
I also have the TSC PHD. It is manufactured by Speeco for them. I purchased mine used and the pin ears, on the boom saddle, had been spread and the holes slightly elongated. Others have posted experiencing the same trouble and have remedied by adding washers to shim out the slop. I utilized a press to straighten the ears. Drilled the holes to 3/4" (or was it 7/8") and installed a Grade 8 bolt with a nylock nut. Other than that, it seems to work well for the little bit I've utilized it.
I also have the deluxe reverse kit. A 48" Ridgid aluminum.