I'm not sure what do you mean by "custom" here but there is Jaxx.io (not open source) which support multiple ERC20 Tokens and there is also coinomi.com which is available on Android only for the moment but iOS is coming soon.
ya asking for a custom whitelabel wallet(works with only one token) is too much to ask for when there isn't much out there that takes all ERC20 tokens and is for mobile.