Featherweight Wheels inserts

I've been working on some wheels for my featherweight which I have 3d printed and threaded with tap and die. Even though I've tested and they've worked as they should, I'm worried about the durability of these threads and I'm looking to redesign the wheel to a design more like this: https://www.youtube.com/watch?v=AcIIUGBJzJM

The question I have is does anyone know where to find these 3/8 (M10) 1-inch length brass hex nuts? I've searches everywhere for 3/8" Hex Female-Female Standoff, 3/8" Hex nut, M10 hex nut, etc and have not been able to find these. All I need is to find somewhere which sells this nut which is to be melted into the plastic.

Thanks, David.

If you search for terms such as "connector", "joiner", "coupler" or "threaded" as well as what you've searched before (3/8, 3/8 BSP or M10) you might get better results, generally the listings don't use the word "nut". You mostly find them used as brake pipe connectors.

I've made wheels using a similar method but just using normal steel ones as they seem to be more widely available than brass ones.

You need to work on your google foo

2 seconds of ebay searching for "3/8 bsp hex"

https://www.ebay.co.uk/itm/1-8-1-4-3...cnQ:rk:18:pf:0

https://www.ebay.co.uk/itm/3-8-BSP-H...Wdg:rk:32:pf:0

https://www.ebay.co.uk/itm/Set-of-5-...Px0:rk:45:pf:0

That's brilliant, thanks very much to you both!