ward floor furnance sight glass

Go to a company that cuts glass for windows. Ask to them if they can cut tempered heat resistant glass like they use in fireplace doors into that small of a circle. Then you need to find that glass or ask if them if they can source it.

I figured someone must still sell parts for these old guys so I searched and found this page: https://www.aberdeenhomerepair.com/...16-p6550.php?retain_errors=Y&retain_notices=Y

The google search term if you want to see more choice: https://www.google.com/search?q=site+glass+for+floor+furnace&ie=utf-8&oe=utf-8

I suspect you will have to buy the glass and fabricate the metal.

I can't seem to find a picture of your furnace and I haven't worked one like that before, but a type of silaca sight glass is used often on some appliances. It looks like plastic, until you touch it. Popular on Engineered-Air units. It might be easier to find if your current sight glass (or hole) is small enough.

Cheers!