Hey Patrick,
What you could do is set up a form specifically to push leads up to SFDC. You would create a form in your Marketo instance, it doesn't need to have any fields on it, and then you would need to grab it and add it to this form code where 'validFormId' is:
<form action="CNAME/index.php/leadCapture/save" method="post">
<ul>
<li>
Client's Email<input type="text" name="Email">
</li>
</ul>
<input display="none" name="munchkinId" value="yourMunchkinId">
<input display="none" name="formId" value="validFormId">
<input type="submit" value="Submit">
</form>
You would also need to replace 'CNAME' with your Marketo Landing Page domain, and "yourMunchkinId" with your munchkin ID. Once you've got a page with this for on it, you'll need to set up a trigger campaign with the Fills Out Form trigger targeting the Marketo form that you created and then a Sync Lead to SFDC flow step.
The effect of this would be that your salespeople would have a simple form that they can submit in order to push a lead up to Salesforce. All they need to do is input the lead's email address and press submit, then the lead would be pushed up.