Thy are gettin pricey (my 2 pence)
Found myself makin my own last Yr. as
I was short on funds and wanted a unique part.
found an used Slipstreamer and customized (cut)
and bought hardware at a home center/harbware store
to make mounts.
There is a good selection on U.S site,you will likely
find similar/same selection.
Last 1 I purchased new about 2000 the price online is
comparable to what I paid 16-17 yrs. ago.