2
Try xDonations
here.
Or to create a custom block with your HTML code, go to System Admin > Blocks & scroll to the bottom of the screen; paste your HTML code in the big box, write the title of the block in the little box, select Visible > Yes & choose the pages you want the block displayed on.
Then, at the very bottom you will see a drop down selection box with "Auto Format", "HTML", or "PHP" - choose HTML. Then hit return.
Then go to System Admin > Groups and enable permissions for guests, if you wish Guests to view the block.
Hope this helps ;)