CB350 exhaust port seals fell out of one side during a ride

[figliolio]

Hello.
I'm searching for knowledge of this piece used to stabilize the exhaust pipe in the engine block.
Where can I find replacements?
What are the ramifications of not having a set of them on one side?
Can I move one of these halves from one side to the other in the mean-time?
Picture:

 

[ancientdad]

Each side needs two of them so moving one only creates the same problem for the other side. Both are necessary to push the exhaust pipe into the head and against the exhaust gasket. Those don't seal the exhaust, as a pair they apply pressure against the larger diameter portion of the header pipe at the end that goes into the exhaust port against the copper exhaust gasket when you tighten the nuts on the exhaust studs against the finned flange. 4into1 and NOS Parts Now both have them for less than most of the first half page of search results

https://4into1.com/genuine-honda-exhaust-collar-18233-318-000-cb350k/

https://www.nospartsnow.com/nos-hon...aust-muffler-pipe-joint-collar-18233-318-000/

Edit: there's also this eBay supplier who offers free shipping for only a slightly higher price for the part, and he has 100% positive feedback

https://www.ebay.com/itm/224814022694

 

[figliolio]

Thank you ancientdad!

 

[CatMan]

If I may ask, how did one of them fall out? Were the bolts loose on the studs?

 

[figliolio]

The flanged collar came loose as seen in the photo above as a consequence of loose bolts so I'd chalk it up to vibrations and me not checking everything is fastened!