A pressure canner isn't a huge investment. Depending on where you live they can be had from around $175 or so. There are cheaper models that may work but in the US I'd say an All American from Wisconsin Foundery is one of the best deals around. All metal, no O-rings to fail or wear out, and really well made.
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“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman