Alf Hagon, what a story he has! If those are gas-charged and stainless steel, and for a 600 lb bike, that should work.
The usual USA replacement is Progressive Suspension (P.S.) 412 series shocks which are < $300 and price dependent on finishes. Search online for these. Star Rider Performance has them for $345.
The better P.S. shock is the 444, and Star Rider Performance has them for just under $800
https://starriderperformance.com/444-series-shocks-85-07-all/
From the above link:
Progressive's 444 Series Shocks are the ultimate suspension upgrade for your 1985-2007 Yamaha Vmax.
444 Series Shocks feature a proprietary patented Frequency Sensing Technology (FST) that has the unique ability to dynamically adjust damping as you ride; what this means is whether you’re hitting the small or big bumps in the road, the shock distributes oil through ports accordingly to soak up the hit making for an ultimately comfortable ride. A top mount threaded preload adjuster allows for fine-tuning with a simple twist of the cap. 444 Series shocks are available in 3 configurations: Standard Weight, Heavy-duty (250+ lbs.) and Super Heavy Duty (Touring Models only - 350+ lbs.).
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There is also the P.S. 430 series, at around $600. See the Star Rider Performance website for info on those or P.S. directly.
There are other suppliers, like Penske and Ohlins, but you are talking $$$$.
Race-Tech sells these, $1,500!
https://racetech.com/
They have fork tubes, fork cartridge emulators, fork rebuild pieces, and much more.