I love reading these stories as buying female clothing is a key part of our right of passage.
As many others have said, the majority of stores are only interested in your money and don't care about who you are or who you are buying for.
What made me laugh, though, is the 'back stories' we dream up in case we are challenged and I can only wonder what goes through the sales assistant's mind as she yet again hears 'I'm buying for a girlfriend/wife - she's about my size'!
At the end of the day, you really don't need a back story - if it's just a case of picking stuff of the rails and taking it to pay, it's completely plausible that your wife has asked you to pay for the things while she goes elsewhere and I'm sure this happens all the time.
For those nervous about taking their first steps, I would suggest the following:
1. Before you start, tell yourself over and over again that what you are doing is completely normal until you believe it. There are many scenarios where males buying/paying for female items are perfectly normal and, therefore, you do not need to justify to anyone else what you are doing.
2. Start with the bigger stores where you can browse without being conspicuous
3. Try to figure out what female size you are before you go. The stores' websites will help you here and asking for a garment in a specific size avoids all of the 'she's about the same size as me' conversations.
4. For things like underwear and shoes (and other items as well if you feel uncomfortable asking specifically for them), go to the stores' websites and print off the pages showing the items you want. Then hand write the size you want on the sheet so that when you visit the store, you can just hand the sheet over and ask whether they have the item.
5. Cosmetics can usually be bought from supermarkets etc. that have self-checkout terminals. Equally, I have not had any difficulties choosing items and taking them to the 'manned' tills.
6. If you're asked, tell the truth! We live in the 21st century where knowledge and tolerance of TG issues is on the rise. I also sense that the majority of female sales assistants would be sympathetic and you may well find that they offer far more help and advice than they would for a run of the mill sale.
Happy shopping!
Amanda