I’d have a look at what size rectangular cast iron grates are available. It wouldn’t need to be a 100% perfect fit especially if the sides are sloped down into the grate. That way if you burn one out you can buy another.
perfectly true,but when you spend £38 + three years in a row on replacements its time to make your own, I found the cast ones where they used to last several years were only just lasting one winter season,presume they are now made overseas from carp, basically melting the centre bars untill the coal fell through, then fire doesnt heat the boiler etc, so I was very pleased that the old tractor bar has worked sooo well.
its not an apollo mission piece but ours is the only heating in the house so needs to be fit for purpose.
make it one time and get on with next job eh.
You can buy new fergie bars..... Maybe they're also not made as well, but you'd hope they'd have to have something decent about them to be sold as lifting/towing equipment.