check ebay, there's a couple of them (steel too);
http://cgi.ebay.co.uk/1950S-RUDGE-WHITWORTH-FULL-OIL-BATH-CHAIN-GUARD_W0QQitemZ170326381280QQcmdZViewItemQQptZUK_sportsleisure_cycling_bikeparts_SR?hash=item170326381280&_trksid=p3286.c0.m14&_trkparms=72%3A1683|66%3A2|65%3A12|39%3A1|240%3A1318
http://cgi.ebay.co.uk/1920S-30S-ROYAL-ENFIELD-FULL-OIL-BATH-CHAIN-GUARD_W0QQitemZ170325365747QQcmdZViewItemQQptZUK_sportsleisure_cycling_bikeparts_SR?hash=item170325365747&_trksid=p3286.c0.m14&_trkparms=72%3A1683|66%3A2|65%3A12|39%3A1|240%3A1318
I'm sure you can modified them to fit your bike?
@edscoble started
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check ebay, there's a couple of them (steel too);
http://cgi.ebay.co.uk/1950S-RUDGE-WHITWORTH-FULL-OIL-BATH-CHAIN-GUARD_W0QQitemZ170326381280QQcmdZViewItemQQptZUK_sportsleisure_cycling_bikeparts_SR?hash=item170326381280&_trksid=p3286.c0.m14&_trkparms=72%3A1683|66%3A2|65%3A12|39%3A1|240%3A1318
http://cgi.ebay.co.uk/1920S-30S-ROYAL-ENFIELD-FULL-OIL-BATH-CHAIN-GUARD_W0QQitemZ170325365747QQcmdZViewItemQQptZUK_sportsleisure_cycling_bikeparts_SR?hash=item170325365747&_trksid=p3286.c0.m14&_trkparms=72%3A1683|66%3A2|65%3A12|39%3A1|240%3A1318
I'm sure you can modified them to fit your bike?