Not a sound idea, Douglas. The 9X19 is a considerably hotter round than .38 S&W with higher working pressures. It's like shooting a proof load everytime you pull the trigger. During WWII,
French partisans would take a 9X19 and slightly peen the rims of the cartridge just enough for the ejector to grab it for extraction. Let me encourage you to NOT to make a practice of trying to shoot 9mm--that's the long and short of it. If you have difficulty finding .38 S&W cartridges try Graf & Sons on the net. They'll mail you a box or two for an all up shipping charge of 4.95 whether you 1 box or 5000 boxes--same fee!
As far as the parts you require, this falls in to the good luck category. Lanyard rings are very uncommon and fetch ridiculous money--as much as 90 dollars on eBay. A Webley Mark IV .38 lanyard ring assembly will work but is equally scarce. The larger lanyard ring for the Webley .455 service revolver will not work in this application. So, all I can do is tell you to watch and buy as you find it. I have found two lanyard rings over the past years and bought both. For some reason, it seems a lot of owners pulled them off back in the 1960's. God only knows why but there you have it. The correct grips turn up on occasion. Expect to pay a good price for them likewise unless you just plain get lucky. I have seen the wooden Mark II grip sell for as much as 125.00 with takers. Recommend you search for a set of Mark III bakelite grips, they should be found for a bit less, maybe 75.00 or so.