Travel grant for summer conference between PhD and first job? I am a PhD student in the US (mathematics) and I expect to graduate in May. 

I got invited to speak in a European conference in June, which is in the awkward time between graduation and my first job (I expect to get a postdoc, and those start August or September). My current department has told me that they cannot fund me after I graduate.

The conference offers some support for young researchers, but it is very meager and I will be flying trans-continentally. I was wondering if there is an outside source that might fund single-conference travel grants for young mathematicians?
Here is a travel grant administered by the Association for Women in Mathematics: https://sites.google.com/site/awmmath/programs/travel-grants/mathematics-travel-grants

Here's one by the Society for Industrial and Applied Mathematics: http://www.siam.org/prizes/sponsored/postdoctravel.php (this requires affiliation with a US university; while your current graduate school and/or future postdoc employer might be unwilling to provide funding they are likely to be more flexible with `affiliation')

I've also heard rumors that a postdoc employer starting in August/September might be willing to support travel in the summer before the appointment starts, but this might just be wishful thinking on my part (but it can't hurt to ask?)