Brief update here, in the interest of sharing information.
I ordered the part set from partssupply.co.uk on 1 March 2017; paid about $32; proceeded to wait the for projected 6 week processing and delivery interim to pass, checking my order status daily.
Having noted no change in the status of my order by 27 March (order status read "Processing in Progress"), I sent an inquiry message noting time passed since date of order.
The reply I received was as follows:
Hello, sorry for late reply. Asked Makita why I still not got handle and they told that they don`t have it in stock now, but I think I will receive it in next week so if you will wait for it I can inform you when it arrives. Is it good for you?
At the start of this thread it is acknowledged that Makita no longer supports this model; I contacted Makita before coming to this forum, before looking at the Parts Supply site, before the proprietor of that site contacted me through this very forum.
Needless to say, I have not heard from Parts Supply UK since my last follow-up message, which read:
I began my search for the part with Makita (i.e.: before looking for another source and finding your online store). The reason I came to you was that Makita has not offered this replacement part for quite some time, and no US aftermarket seller had it in stock (not to put too fine a point on it, but your website lists the part as being in stock).
If you have a source about which I don't know, that will be heartening news. If not, I hope we can find a way to rectify the apparent error.
I guess that's about it.