I thought I'd post some quick pics of a bracelet swap that I did a while back on my 6138 Jumbo. This started as an all original 6138-3009 with a production date from May, '72 (which I decided could be a "birth year" watch for me since its the year the Mrs. was born). It had a badly scratched crystal, but the case, dial, hands and movement were all great, and it came with the original president bracelet (which has some moderate stretch but is still in nice condition). It had never been serviced when I received it, so I had the movement overhauled and an NOS crystal installed. The watch head on these 6138s is 42mm, with 19mm lugs, so I decided to test a 20mm H-Link bracelet not getting worn on my SARX015. It took minor widening of some 6105 hollow end links from Larry (UncleSeiko) to get the 11mm center link to pass through. The solid link bracelet really balances the weight of the large case, and makes it great for daily wear.
I believe there is an UncleSeiko H-Link bracelet for 6139s now that is more faithful to the original Stelux (and the East Tech H-Link), so I would assume these same 6105 end links are the closest fit for you to mod and use his H-Link on a 6138.
I know it's not for purists, but hope other 6138 fans appreciate the look of this new style Seiko H-Link, too. Tom