I searched for quite a while for a replacement rack and pinion.. I could not find one other than the ridiculously priced replacement from American Landmaster. I ended up rebuilding mine. It was not to bad to get apart. the housing , gear and steering gear bar were in good shape. the problem was finding spacers that would hold the steering gear bar straight and let it move side to side. I went to a local Hardware Supply that only sold nuts, bolts..etc. They had some spacers that fit perfectly. across the street from that place was a bearing place. They had oils seals that fit the open end perfectly. After I got the steering box greased and assembled I hammered in the oil seal at the end to hold it all together. I was worried the oils seal may come out with use, but months later and lots of riding it never moved. All the parts were around $25. The rebuild was cheap and easy once I secured the correct spacers and seal.. The spacers were loose bulk and the bearing place opened the bag on the seal to look at the fit. When I bought everything I did not get any part numbers or sizes. The part on mine that was really worn was the steering shaft. The end that connects to the steering box was completely rounded out. I ended up making my own steering shaft with two steering shaft ends and a piece of steering shaft. It was much higher quality and would never strip out. But, for the same money I could have just bought the overpriced new shaft from American Landmaster. It would have been much easier.
As far as other parts.... Anything that is specific to the Bulldog can only be found through American Landmaster and some of those parts are no longer available. The Frame and Plastics: Fenders, roof, bed..etc are all oem parts. I bought those from Tractor Supply. They used to be an American Landmaster dealer until last year. They were much cheaper than American Landmaster and if I had them shipped to the store for pick up there was no shipping. You need to search Google for dealers selling these parts. Sometimes you will find old stock cheap. You can also use parts from different models that are actually the same part. American Landmaster will give the parts a different model number for the same part. Example: The rear fenders for a Bulldog are sold individually at a ridiculous price $60+ and high shipping cost. That is $120+ Shipping. Yet the rear fenders for the 265 model ( The cheaper version of the Bulldog ) are sold by the pair for $39.99 and can be found on Ebay sometimes with free shipping. They are exactly the same part. As for mechanical parts, most of them are Golf Cart and Go Kart parts. It takes some searching to find the correct parts. Most I found were E-Z-GO Golf Cart parts.
If you have a specific part you are looking for and I bought the same one, I can look to see if I have the info. I bought the majority of mechanical parts on Ebay and Amazon.