Have you tried Googling with the part number and manufactor. You should be able to download a manual with the part numbers. Then it's just a simple matter of Google the part number you need.
If you can find them online using the make and model number, you might for universal knobs that many appliance outlets sell. Even Amazon.
Here's some at Ace:
http://www.acehardware.com/product/index.jsp?productId=1279536
eBay
https://www.ebay.co.uk > ... > Slow Cookers
Buy Tower Slow Cookers and get the best deals at the lowest prices on eBay! Great Savings & Free Delivery / Collection on many items.
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The are 4 , 5, or 6 Quarts. This is a little known brand called Royal from China. If you have one, just take a measuring jug, or a pint beer mug and add water. A 'quart' is 2 pints.
If you are thinking of buying one, run away!
https://www.google.com/search?q=Smart+Pot+SC22
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If timing does not allow the recipe to be cooked on low for as long as required, the slow cooker can be turned up to high and the cooking time reduced. Convert cooking time by using a ratio of 2 hours of cooking on low as being equal to 1 hour of cooking on high.