If it doesn't already exist, how can we use the BitPay's Exchange rates [ https://bitpay.com/bitcoin-exchange-rates ] as a means of automatically pulling a current BTC exchange rate for presenting BTC prices to shoppers in OpenCart [ http://www.opencart.com ].

I ask, because I have the BitPay payment extension [ https://github.com/bitpay/opencart-plugin ] set up, but this doesn't provide a means of automatically pulling a current BTC exchange rate for presenting BTC prices to shoppers.