It's a bit convoluted, but yes you can buy any parts you want to from the Trumpeter replacement parts department. I've answered this question so many times on Facebook an various post you would think I would have is saved on my computer...jarndice wrote: Is there a site where I can purchase a "Trumpeter Rack"?
So the process is: find out the Trumpeter kit number, find out the sprue letter/number you want to order, contact joanna@trumpeter-china.com with the information about what you want to order, she will send a Paypal address to make payment, and then wait weeks for the part to arrive.
In my case I wanted the extended bustle from Trumpeter so I specified the M1A2 kit 00927 sprue H. Sprue cost me $3 US with $10 shipping ($13 US total). I'm sure prices are higher now because that is 2019 pricing.
Just saved this post on my computer for the future.