Thanks for your interest, Smokey and Hansang. I have a 1st gen Vive, but intend to get a Reverb once HP sorts out the supply issues due to the superior resolution. I'll take a look at the Gat App tech video. I found this "high grade replica" on eBay which might be an alternative:
https://www.ebay.com.au/i/223420899888?chn=ps&norover=1&mkevt=1&mkrid=705-139619-5960-0&mkcid=2&itemid=223420899888&targetid=539012170959&device=c&adtype=pla&googleloc=9071322&poi=&campaignid=1669165661&adgroupid=68573517350&rlsatarget=pla-539012170959&abcId=578876&merchantid=116551715&gclid=CjwKCAjwxrzoBRBBEiwAbtX1n2EGv70ikEQOyWmfOnAK-PEjc4y5Es6-ze4NJDRgardOd8Q3CTayqxoC7DsQAvD_BwE
It looks a lot wider at the front, or at least has a lot more padding that can be removed or compressed. It's also a lot cheaper than a genuine HGU. Doesn't look as cool as the genuine article of course, and the remark in the description that: "Even so, some friends may feel that the helmet is too tight. This is a normal phenomenon." is somewhat concerning. Still, might be a decent option B.