Tickers beginning with a number

[szabootibor]

Some tickers begin with a number, e.g. CD Projekt SA: 7CD

These are not accepted by Beancount as a commodity name:

2021-03-30 * "7CD" "BUY 40 7CD @ 47.68 EUR"
  Aktiva:Invest:Aktien:IB           40 7CD {47.68 EUR, 2021-03-30}
  Aktiva:Invest:IB:EUR         -1907.20 EUR                       
  Aktiva:Invest:IB:EUR            -1.25 EUR                       
  Ausgaben:Invest:Gebühren:IB      1.25 EUR                       

syntax error, unexpected NUMBER, expecting end of file or EOL or ATAT or AT

So a mapping of such tickers to acceptable commodity names would be needed. I have actually no better idea than using a prefix.