There are many people out there who are single mothers. If you are financially secure, you'll be fine.
I know a woman who, like you, wanted a family and didn't meet the man of her dreams. She adopted two children from Thailand, she has a full-time job and she hired a helper. And they are all very happy together.
Regarding your "sperm" situation... hhhmmm, don't know anything about that!
I wonder... will I get brutally shot down by suggesting picking someone up in Wanchai and then never seeing them again...? ;-)
If that's not your thing... here's an article on Sperm Banks. Seems there's one at the Sanotorium Hospital, but maybe it's only for couples and it could be costly.
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Another option is to freeze your eggs and save them for later... in the hope that you do eventually meet someone.