Thanks David. You might be correct. 2215 and 2213 which I checked, has the same cover with part number 200-2520-00. I have not checked the others in the series though.
They seem to be very rare except for the one I have seen on eBay at quite a shipping cost! Even if it is cracked, it is still OK as I can always repair and give it a coat of paint.
Hope someone will have one of these things.
I have 2230 and 2232 oscilloscopes, and I know they use the 2235 cover which is the same as the cover for the 2213A/2215A, 2221/2221A, 2224, 2236, 2235A/2236A. These models are all descendants of the 2235.
The 2213/2215 came before the 2235 and are not really the same series, but they might use the same cover.
The 2225 series came later, and might also use the same cover.
When I was searching for covers on Ebay, I checked both by model number and by dimensions. A couple that I bought had cracked corners so I repaired them with plastic cement and polystyrene strips as shown below. The covers look dusty in the photos because of sanding.