Various people have made their own, or a few. I only know of one who has made quite a number now, for customers:-
www.sdmtelescopes.com.au
Various of these also come up for sale second hand, from time to time if you are patient.
You can buy truss dobs from overseas (USA mostly), but shipping will be significant. There are kit makers overseas which might reduce shipping costs, but you would need to fit them out yourself with mirrors, focusser etc.