How to custumize Subscribe button in subscribe2 plugin?

How do I customize the Subscribe button in the Subscribe2 sidebar widget so it is the same as my Search Blog button?

Both buttons are located in my sidebar. The Search Blog form is about halfway down in my sidebar, and the Subscribe form is all the way at the bottom: https://blog.cyberquill.com

Right now, the Subscribe button is a generic gray Input button, and the code in subscribe2.php for the Subscribe form goes like this:

$this->form = "<form method=\"post\" action=\"\"><input type=\"hidden\" name=\"ip\" value=\"" . getenv('REMOTE_ADDR') . "\" /><p>" . __('Your e-mail:', 'subscribe2') . "<br /><input type=\"text\" name=\"email\" value=\"" . __('Enter e-mail address...', 'subscribe2') . "\" size=\"20\" onfocus=\"if (this.value == '" . __('Enter email address...', 'subscribe2') . "') {this.value = '';}\" onblur=\"if (this.value == '') {this.value = '" . __('Enter email address...', 'subscribe2') . "';}\" /><br />

<input type=\"submit\" name=\"subscribe\" value=\"" . __('Subscribe', 'subscribe2') . "\" />

</p>
</form>\r\n";

My Search Blog button has the following custom code:

<a class="searchsubmit" href="javascript:document.search_form.submit();">Search Blog</a>

“searchsubmit” is the CSS class for my Search button. I’d simply like to apply the same class to the Subscribe button.

The chunk of code responsible for the current (generic) Submit button seems to be this:

<input type=\"submit\" name=\"subscribe\" value=\"" . __('Subscribe', 'subscribe2') . "\" />

How do I have to modify this chunk of code to display a custom Submit button that looks the same as my Search Blog button?