Is there a 'Buy me a Beer' button for wordpress.com blogs?

I want to add the ‘buy me a beer’ button to my wordpress.com blog but it is only available for wordpress.org blogs, and I do not want a wordpress.org blog. Is there an html code for the buy me a beer button? If not, is there a donation button for Facebook (not a paypal button, because my account is personal)
I found a button code but it displays my merchant ID. Is my Paypal Merchant ID like a password and extremely sensitive?