I might have a solution for you, I am using a keyboard tray that doesn't
slide on runners,  the tray is screwed onto central  arm that is attached
under the desk, the tray that came with unit is 20 1/4" long, but you could
cut it to 18" long.  Or better yet perhaps the manufacture could make a
smaller tray.
Here is the address and phone numbers from the back of the pamphlet:

tray:  The Freedom Arm

Neutral by Design
Two Fox Pointe Centre
Suite 100,
6 Denny Road,
Wilmington, Delaware, 19809
302-762-7226
800-400-0625
Fax: 302-762-9210

I bought my tray from McCrum's Office Furnishings  in Calgary, Alberta,
[log in to unmask],   403-255-3315

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