I've been watching this market change rapidly since the early 1970s.
Manufacturers come and go. Equipment is usually ordered direct from
the maker, freight extra. Those interested in large horsepower
shredder/chippers might check the advertisements in garden-related
magazines such as _National Gardening, Organic Gardening, Sunset,
Horticulture, Fine Gardening, Country Living (Harrowsmith), _etc.
Without intending any endorsement or criticism of their products,
two makers that have remained in business since I started gardening
are:
Kemp Company. 160 Koser Road., Lititz, PA 17543. (also compost
drums)