I'm tasked with redoing part of the UI in one of our desktop applications. I've specifically been asked to replace a "Load" button with an icon. Are there any conventions for this style of icon? Unfortunately, it's not a straightforward "open file" button, so the standard Windows icon won't work here (and would be confusing, as one of those icons already exists in the same space).

The load button (pictured above) shows a dialog to the user prompting for a source, then loads a list of things from the datasource (either a database or a file of some sort) into the combobox to its right (which then becomes active).
The button can be clicked again, allowing the user to re-load different information into the combobox.
We were thinking of perhaps going with the recycle icon, but that isn't intuitive in terms of communicating that it also functions as the initial load (as well as reload). We were also considering some sort of arrow, but we're not sure how well that would represent "loading".
One thing to note is that the button could be relocated to the right side of the combobox if that is a better design. The UI contains multiple instances of this button-combobox pattern.
And also, just to clarify: this is a desktop app, so no uploading is required (the file / database is already on disk).
[EDIT] If there is no convention for the load icon, what would you suggest?
What happens when the user clicks load:
The user clicks Load. A dialog opens, asking the user for details about the datasource from which to load (database, file, etc.). When the user clicks OK on the dialog box, the program reads the data from the source and populates the combobox. For more information about how the combobox is used, see my other recent question.
The combobox looks like this after the data is loaded & it is enabled:



