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Where are you...
Here is a link to a product at a site in Australia that is competatively priced, but may be too much for your needs. You can pour out and only mix up what you need, however, once opened it won't last the otherwise (I believe, but stand to be corrected) 2 year shelf life.
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With any of these products excess hardner addition will typically result in a higher cure temperature with resultant shrinkage which you don't want.