You can have them welded up, obviously depending on the size shape and condition of the crack. I would only consider this option if you get it professionally done. Otherwise you could either source secondhand or new legs. New parts are still available and will be for some years yet as all manufacturers have agreed to (under EU directive) to supply OEM parts for vehicles that have been out of production for up to 15 years.

http://ec.europa.eu/DocsRoom/documents/10705/attachments/1/translations/en/renditions/native

Obviously outside the EU different rules apply.

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