So little time!

Someone told me that prom shops are a great place to find reception dresses! Also, can’t go wrong with online shops. You can find a lot for under $100.00, buy two sizes and send whichever one doesn’t work back! Best of luck shopping!

A lot of places that sell prom dresses usually have white ones. Also if you go to a shop and buy your size off the rack you don't need to have it ordered and shipped.

Check Lulus and ASOS, both usually have a lot of choices and reasonable prices. They both ship pretty quickly so that shouldn’t be a problem.

Check with David’s Bridal or call around to local shops to see if they have off the rack dresses. I would do this ASAP in case you need alterations

Try looking at white pageant dresses. There are some amazing ones even in the 300-550 range. Sherri Hill, Jovani.

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This is my other suggestion. They have gorgeous pieces as well!

I just bought this dress from Fashion Nova for less than $50! It hasn't come in yet so idk how it would fit but it has great reviews!

And then there are these options under $300 with corset back.
$218
https://www.unique-vintage.com/products/white-strapless-lace-crystal-bridal-dress
$96
https://www.unique-vintage.com/products/off-white-chiffon-strapless-sweetheart-corset-long-gown-1
$290(white and ivory)
https://www.unique-vintage.com/products/white-embellished-strapless-mermaid-bridal-gown
$96
https://www.unique-vintage.com/products/cream-chiffon-strapless-sweetheart-corset-long-gown

Lulus!

Or look into white bridesmaid dresses.

BHLDN has a dress section specifically for "last minute brides", maybe you could find something there?