Modify the below page to suit your needs. There’s no php, it’s straight HTML, so it should work on any page.
<div id="login">
<h1><a href="https://www.ads-software.com/">WordPress</a></h1>
<form name="loginform" id="loginform" action="https://domain.tld/wp-login.php" method="post">
<label>Login:<input type="text" name="log" id="log" value="" size="20" tabindex="1" /></label>
<label>Password: <input type="password" name="pwd" id="pwd" value="" size="20" tabindex="2" /></label>
<p class="submit">
<input type="submit" name="submit" id="submit" value="Login »" tabindex="3" />
<input type="hidden" name="redirect_to" value="wp-admin/" />
</form>
<ul>
<li><a href="https://domain.tld" title="Are you lost?">« Back to blog</a></li>
<li><a href="https://domain.tld/wp-register.php">Register</a></li>
<li><a href="https://domain.tld/wp-login.php?action=lostpassword" title="Password Lost and Found">Lost your password?</a></li>
</ul>
</div>
Edit https://domain.tld
to point to your WordPress directory. Btw, this code is ripped directly from wp-login.php after you view it at the login window.